[3.6] Add missing .gitignore entries for VS2015 IntelliSense DB (GH-1223) (#1225)

(cherry picked from commit 8e675286a92f33837cfffac5914b5175dac5d573)
diff --git a/.gitignore b/.gitignore
index db27597..9392fe5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -52,6 +52,8 @@
 PCbuild/*.*sdf
 PCbuild/*-pgi
 PCbuild/*-pgo
+PCbuild/*.VC.db
+PCbuild/*.VC.opendb
 PCbuild/.vs/
 PCbuild/amd64/
 PCbuild/obj/